According to cosmological simulations [1]}, the IGrM has
the greatest potential to show a rich variety of ion species. O VIII
should be the most detected species within group virial radii, while O
VII should be detected in lower mass groups at \(M_{500}10^{13.5}M_{\odot }\) . In its main mission, Arcus should detect the
\(T=10^{5.4-6.8}\)  K IGrM in at least 10 group haloes at a 3 m\(\mathring{A}\) 
equivalent width threshold (at \(5\sigma \) ) for O VII and O VIII.
Interestingly, the Fe XVII should be detectable within \(R_{500}\)  for
groups, probing gas up to \(\approx 10^7\)  K for at least 5 group
haloes. Integrating longer on the brightest X-ray quasars opens up
the possibility to detect more species using a 1 or 2 m\(\mathring{A}\)  detection
threshold, including Ne IX and Ne X. C V and C VI (and maybe N VII)
may also be detectable in the group outskirts for deeper observations
probing gas down to \(10^5\)  K. Sensitive UV absorption line
spectroscopy brought about by the Cosmic Origins Spectrograph on Hubble discovered that the objects with the richest and most diverse
set of species probing gaseous halos are star-forming, \(L^*\)  galaxies
[2]}. It is expected that groups will be the analogous
richly detected, multi-species objects to be probed via X-ray
absorption line spectroscopy.
